Monitoring of the Lung Fluid Movement and Estimation of Lung Area Using Electrical Impedance Tomography

Abstract

It is very essential to visualise the internal condition of human body not only for studying the anatomy and physiology, but also for diagnosing a disease. Physicians always try to analyze an organ or body part in order to study its physiological and anatomical status for understanding and/or treating its illness. Thus, it is always requisite to introduce the diagnostic tool called medical imaging. The period of medical imaging started in 1895, when Roentgen discovered the powerful invisible rays called X-rays. Gradually the medical imaging introduced X-Ray CT, Gamma Camera, Positron emission tomography (PET), Single-Photon Emission Computed Tomography (SPECT), Magnetic Resonance Imaging (MRI), and Ultra SonoGraphy (USG). Recently, medical imaging field is more advanced with comparatively newer tomographic imaging modalities like Electrical Impedance Tomography (EIT), Diffuse Optical Tomography (DOT), Optical Coherence Tomography (OCT), and Photoacaustic Tomography (PAT). The EIT has been extensively researched in different fields of science and engineering due to its several advantages. In correlation with the application of the EIT in the medical field, thoracic electrical impedance tomography (EIT) is used to diagnose patients suffering from the acute respiratory distress syndrome (ARDS) for monitoring their conditions ranging from dynamic shifting of body fluids to lung aeration, right at the bedside. Moreover, EIT-derived numeric parameters would help the physician to evaluate the state of the lung of a patient under observation. Thus, here we have performed a Finite Element Method based simulation study for monitoring the condition of lungs and heart of ARDS patients. Therefore, a finite element method (FEM) model of human thorax in three dimensional platform with FEM Multiphysics software is created and tested with new ventilation indices regarding their ability to quantitatively describe structural changes in the lung due to the gravitationally dependent lung collapse. Additionally, analysis is made to find the electrode pairs capable of separating the lung and heart activity when a particular amount of constant current is injected through them, are also carried out. Finally, a real time EIT system using 16 Ag-AgCl electrodes are developed to get the image of human thorax. The data are collected using the adjacent current injection technique and are plotted using FEM Multiphysics software. The reconstructed FEM images using the forward solver of EIT method shows the approximate area of the thorax (lungs, heart etc.) under observation. This chapter will present a brief overview on application of EIT for monitoring of the lung fluid movement and estimation of lung area in a human being alongwith physical and mathematical aspect with a goal to achieve a system having higher potential to cater medical challenges in lung oriented diseases.